OK - Here's the scoop. I was shocked to find the local dealer had one in stock so I picked it up on the way home.
Firstly, I checked the Amp PN on my 06 SEUC and it's 76192-06A - Not the 76418-06(A) (new number is 76000068) they warn against. The reason the amp is involved isn't the physical install. Evidently the radio and/or amp has a built in EQ that cuts the lows below a certain frequency to avoid frying the speakers on the low end. The last step in the install is to have the radio reflashed with a free download to increase the low range. That took me by surprise. Now the question is, is 76192-06A the same as 76418-06(A) or will this flash work with my amp??? Both are versions of the 40x4 HO Amp, so it's a big question mark. Naturally, the dealer had no clue, so before I start hacking away, I'm going to call HD tomorrow and sort this out. I'm not even sure I'll reach someone who can answer this so this might turn into a crap-shoot.
Regarding the install itself, although nothing really lines up correctly with the template for the holes on the leather tourpak, after laying everything out, I think it'll work. You have to remove the speakers and the switches - essentially all of the wiring out of the speaker pods, so that you don't snag anything when drilling the holes. You drill the 2" hole through the tourpack to the rebolted pods, then remove the pod, insert the liner, and drill from the outside in to get the liner hole lined up.
Then bolt everything back together, using the suppled gaskets, and hope that the ports are long enough to make it through the thicker CVO liner. In theory, it should help, and every little bit helps.